The subject technology is a novel miniaturization of a packaging system known in the electronics industry as an air transport rack, or ATR. These rack standards were initially used for radio equipment deployed on WWII aircraft. Over the years, these rack standards were adapted for packaging of digital computer components, in a similar class of service. A full ATR box has the following dimensions: width=25.7 cm, length=49.6 cm, height=19.4 cm.
Contemporary ATR boxes come in two lengths, long (49.6 cm) and short (42.0 cm), and come in a variety of widths, defined as a fraction of the width of a full ATR box. The widths include: 1 (25.7 cm), ¾ (19.1 cm), ½ (12.4 cm), 4/8 (9.0 cm), and ¼ (5.7 cm). A typical small ATR form factor is the “one half, short ATR”, and is used to package 3U Euro-standard slot cards (least reparable units, LRUs).
As electrical components become increasingly miniaturized, however, the volume of even a quarter ATR box is needlessly large, and not only takes up valuable space within an aircraft but also contributes unnecessary weight. Furthermore, miniaturization of electrical components is often accompanied by an increase in power density and attendant thermal effects. Thus, simply packing more components into less space is an unworkable solution unless the problem of heat dissipation are also solved.
Conventional approaches to the problem of heat dissipation rely on air-cooling or water-cooling to dissipate the heat generated by densely packed electrical components. These approaches suffer significant weaknesses, however. Air cooling requires additional components, such as fans, filters, etc., that increase the cost and weight of the unit and which are additional components that may fail. The failure of a fan in particular can have a disastrous effect on the system operation. Water or liquid cooling is similarly expensive, heavy, and includes additional components that may fail.
Another conventional approach includes using heat spreaders to disperse heat away from the electronic components, usually to a heat sink. However, conventional systems that use heat spreaders suffer a significant weakness, as well: the heat spreader is coupled to the heat sink via the relatively small contact area of circuit board edges, which fit into shallow grooves in the heat sink. One popular approach uses Wedge-Lock® retainers, which are mounted to the printed circuit boards and are then inserted into channels machined into the cold plates or heat exchangers. The Wedge-Lock® system incurs some mechanical overhead, because the locking adapter must be mounted to the PCB and also because the system requires machined channels into which the locking adapters are inserted. As modules are scaled to smaller dimensions, this overhead becomes a larger and larger percentage of the total hardware. In addition, the contact surface through which heat may be transferred from the PCB to the cold-plate is limited to the width of the locking adapter portion, which limits the amount of heat conventional systems can dissipate. Because of the relatively small surface area provided for heat transfer, Wedge-Lock® systems have very high flux density. Moreover, as overall chassis volume is reduced, the Wedge-Lock® scheme does not scale at the same rate, thus occupying a relatively larger overhead, relative to the net available payload. In short, Wedge-Lock® systems are cumbersome, take up space, and are a potential point of failure.
Accordingly, in light of these disadvantages associated with conventional ATR boxes, there exists a need for a compact ATR form factor that includes enhanced thermal management capability. Specifically, there exists a need for a printed circuit board module enclosure and apparatus using same.